The present invention relates in general to pressure sensors, and, more specifically, to a redundant safety switch for detecting the presence of pressurized fluid.
Compressed air systems are used in many industrial settings to operate various types of pneumatic actuators. Air is compressed by a compressor and delivered to the actuators via a distribution system including conduits and valves. Some systems may cover a very large area with one or more high capacity compressors pumping compressed air or other fluid into an extensive network of delivery conduits. The network may include sections that can be isolated from the compressor(s) by closing certain valves. This allows portions of the system to be disassembled for maintenance or other reasons.
Prior to attempting to disassemble or service a pneumatic system, it is necessary to ensure that the supply of pressurized fluid is removed from the point in the system being accessed. Various safety standards and governmental requirements exist, such as European Standard EN954, which direct that a pressure monitoring device be used to avoid unsafe servicing operations.
In certain applications, it may be necessary or desirable to perform redundant monitoring so that the failure of one monitoring device does not lead to attempted servicing at a point still receiving line pressure. A pressure switch is one typical type of monitoring device. Deploying redundant sensors has typically required the mounting of two separate pressure switches, more than doubling the cost of obtaining the safety function.